The invention relates to valves used in controlling the flow of fluids in a fluidic system and, more particularly, to a valve and components thereof suitable for use in high temperature, corrosive, abrasive, and other hostile environments.
Valves are commonly employed as flow control devices in all types of fluidic systems. These valves may have many different configurations, depending on the particular application, such as a ball valve, a gate valve, a globe valve, a slide valve, a check valve and the like. Such valves typically comprise a housing having a fluid inlet and a fluid outlet, a flow-control element disposed within the housing between the inlet and the outlet, seals engaging the flow-control element to prevent the fluid from flowing between the housing and the flow-control element and/or out of the housing, and an actuating device for moving the flow-control element between an open position, where flow of the fluid between the inlet and the outlet is permitted, and a closed position in which the fluid is not able to flow between the inlet and the outlet. These components of a typical valve are generally comprised of materials appropriate for the particular application. For example, many components for a low pressure cold water valve can be comprised of a polymer material, whereas a higher pressure steam valve may be comprised predominantly of metallic components. However, common valves generally become unsuitable as the temperature and the hostility of the environment increases. For instance, where corrosive and/or abrasive-containing fluids are being handled, commonplace valves may be easily damaged unless special measures are taken in the design of the valve and/or the remainder of the fluidic system to protect the valves. Without costly measures to allow the use of commonplace valves in hostile environments, a serious safety hazard or reliability problem may be created. As a further example, high temperature fluidic processes typically require hot process fluids to be cooled before being pumped or piped to a subsequent location where the fluid may again have to be restored to the proper operating temperature for the process, thereby reducing the efficiency and raising the cost of such an operation. Thus, there exists a need for a valve capable of operating safely, reliably, and economically in high temperature or other hostile environments, such as in fluidic systems where corrosive and/or abrasive-containing fluids are present.
Still further concerns exist with common valves in emergency situations where the temperatures of the fluids to which the valves are exposed are not controllable. For example, in the event of a fire at a petrochemical refinery, excessive temperatures may cause common valves to fail, thereby allowing storage tanks to deleteriously feed the fire with catastrophic results. At excessively high temperatures, seals internal to the valve may fail, the seat and/or the flow-control element may warp, and/or any springs present within the valve may lose their spring constants and thereby allow separation of the components biased by the spring. Thus, the endeavor to develop a valve suitable for use at excessively high temperatures has led to the proposal that ceramic materials could be used for valve fabrication. See, for example, U.S. Pat. No. 4,372,531 to Rollins et al.
Ceramics are generally recognized as a class of refractory materials suitable for use in high temperature applications and in corrosive or abrasive environments. However, most ceramics are typically deficient in their ability to withstand tensile stresses without failure. Therefore, where components are fabricated from ceramic materials, these components are configured and utilized such that they are exposed mainly to compressive stresses and little or no tensile stresses. However, many components of a valve may experience significant tensile stresses due, at least in part, to shear stresses imparted by the fluid and possibly the configuration and utilization of the component. Thus, where ceramic has been utilized in the fabrication of valve components, additional measures must often be taken to assure that the valve functions as intended without the ceramic components failing. Generally, these additional measures comprise supplemental components fabricated of a material more appropriate for withstanding tensile stresses, but typically not as able to withstand excessively high temperatures as the ceramic material. For instance, a TEFLON(copyright) seal may be placed between the flow-control element and the seat. This results in a valve where the critical and/or fluid-contacting components are not entirely able to withstand excessively high temperature or other hostile environments to which the valve may be exposed. Thus, there exists a further need for a valve capable of withstanding high temperature or other hostile environments, wherein the critical and/or fluid-contacting components are fabricated of refractory materials such as a ceramic, preferably with as few seams as possible therebetween.
Thus, a continued need exists for a practical valve capable of withstanding excessively high temperatures or other hostile environments, wherein the valve is relatively simple to produce, reliable, and cost effective.
The invention comprises a flow-controlling device for controlling the flow of a fluid, a valve, capable of withstanding extreme temperatures of over 400 degrees Centigrade and also capable of withstanding abrasive and corrosive environments. All of the urging and sealing components in the valve, including the flow-control element, the seat sealingly engaging the flow-control element, and the means for urging the seat into sealing contact with the flow-control element, are prepared from highly stable refractory and/or toughened ceramic materials that are capable of withstanding abrasives, corrosives, and extreme temperatures. No resilient materials including metal, rubber and rubber-like polymers, TEFLON(copyright), or o-rings are included in the valve. The valve components are simple in design and can be retrofitted into an existing standard valve design, including, but not limited to, poppet and ball valves. These valves can withstand process fluids at over 500 degrees Centigrade, at over 640 degrees Centigrade, and at red hot conditions of 1000 degrees Centigrade or more over extended periods of time comparable to similar designs at current practical limits of about 200 to 400 degrees Centigrade.
Certain refractory and/or toughened ceramics materials, commonly referred to as advanced ceramics, exhibit useful resistance to tensile stress when the material is heat treated in a certain manner. More particularly, a yttria-stabilized zirconia or other comparable ceramic material that is fully annealed so that porosity in the material is minimized and so that the material is substantially homogenous, is capable of substantial elongation and compression without failure. This flexible ceramic allows the fabrication of fluid-contacting, sealing, or other members from the same heat and wear-resistant materials.
The above and other needs are met by the invention which, in one embodiment, provides a flow-controlling device for controlling the flow of a fluid prepared in accordance with the invention. The device comprises a housing, a flow-control element disposed within the housing, at least one seat operably engaging the flow-control element, and a biasing device operably engaging each seat for urging the seat into sealing engagement with the flow-control element. Each of the flow-control element, the seat, and the biasing device are comprised of refractory and/or toughened materials including, for example, an advanced ceramic. More specifically, the seat, the flow-control element, the biasing device, or other components may be advantageously fabricated of a flexible ceramic material. In some embodiments, the seat and the biasing device, including a spring, are prepared as a unitary structure from a toughened ceramic, including, for example, yttria-stabilized zirconia and others. The flow-control element can be prepared from a harder ceramic, if desired.
The flow-controlling device of the invention further comprises an actuating device operably engaging the flow-control element. A housing for the device generally defines an inlet adapted to receive the fluid and an outlet adapted to dispense the fluid. The flow-control element is disposed between the inlet and the outlet and is adapted to control the flow of the fluid therethrough. The seat operably engages the flow-control element and is adapted to prevent the fluid from flowing between the housing and the flow-control element.
In one advantageous embodiment of the invention, the seat is further adapted to channel the fluid between the flow-control element and at least one of the inlet and the outlet. The biasing device operably engages the seat and urges the seat into a sealing engagement with the flow-control element. The actuating device actuates the flow-control element, with respect to the seat, between a position in which flow-control element allows the fluid to flow between the inlet and the outlet and a position in which fluid-control element does not allow the fluid between the inlet and the outlet. If desired, the actuating device is also be prepared from the same types of materials as the flow-controlling element, the seat, and the means for urging the seat into sealing engagment with the flow-control element.
In an alternative embodiment, the sealing device may further comprise a shield operably engaging the seat and adapted to channel the fluid therethrough such that the fluid does not contact the biasing device. This embodiment can be useful if it is desired to preclude contact between abrasive particles and a helical coil spring prepared from ceramic materials. However, it normally should not be necessary to isolate the spring from the abrasives that may be contained in a process fluid. Of course, if the valve were operated at lower temperatures, then a spring made from materials meeting the temperature requirements could be substituted. If desired, the seat, the biasing device, and the shield are integrally fabricated from a unitary piece of a ceramic material.
The invention includes a method of fabricating a sealing device for interacting with a flow-control element of a flow-controlling device for controlling the flow of a fluid. First, a bore is formed in a cylinder of a refractory material such that the bore defines an axis and is adapted to cooperate with the flow-control element to control the flow of a fluid through the bore. In some instances, the sealing device may be fabricated from a tubular member having appropriate inner and outer diameters. A groove is then formed about the perimeter of the cylinder such that the groove is concentric with the bore. A seating surface is then formed in the cylinder adjacent to the groove and generally perpendicular to the axis of the bore. The groove is disposed proximally to the seating surface so as to cause the portion of the seating surface about the perimeter of the cylinder to be flexible. A channel is then formed in the cylinder opposing the seating surface, wherein the channel extends into the cylinder concentrically with the bore, and thereby forms a spring blank outward of the channel and a spring shield inward of the channel such that the spring shield houses the bore. A spiral groove is then formed in the spring blank so as to fabricate a biasing device. In this manner, the sealing device is formed as an integral structure from a unitary piece of a refractory material, such as a ceramic, where the biasing device is capable of urging the seat into sealing engagement with the flow-control element and the spring shield channels the fluid flow such that contact of the fluid with the biasing device and/or the housing is avoided.
Still another advantageous aspect of the invention comprises a device for sealing an actuator that is operably connected to a flow-control element disposed within a casing of a flow-controlling device for controlling the flow of a fluid. Generally, the device comprises a housing adapted to engage the casing so as to surround the actuator, a compliant packing adapted to be disposed about the actuator, an end cap operably engaging the housing, and a biasing device disposed within the housing intermediate the end cap and the packing. The housing has a proximal end adjacent to the flow-control element and an opposing threaded distal end. The packing is disposed about the actuator at the proximal end of the housing adjacent to the flow-control element to form a seal between the actuator and the housing. The end cap is secured to the threaded end of the housing and is generally adapted to allow the actuator to pass therethrough. The biasing device is configured such that a substantially uniform compressive force is applied to the packing about the actuator when the biasing device interacts with the end cap and the packing. The packing is thereby compressed between the housing and the actuator to form a seal therebetween. The packing can be comprised of, for example, a graphite-impregnated foil material or a graphite-impregnated ceramic fiber. The actuator and biasing device can be prepared from ceramic materials of the same type as is used in the other components, if desired.
In one embodiment, the invention comprises a ball valve for controlling the flow of a fluid. Generally, the ball valve comprises a housing, a valve ball disposed within the housing, at least two seats operably engaging the valve ball, a biasing device operably engaging each seat, optionally a shield operably engaging each seat, and a valve stem operably engaging the valve ball. The housing defines an inlet adapted to receive the fluid and an outlet adapted to dispense the fluid, wherein the valve ball is disposed between the inlet and the outlet and defines a bore capable of establishing communication between the inlet and the outlet. The seat is adapted to prevent the fluid from flowing between the housing and the valve ball, while the biasing device operably engages the seat and urges the seat into sealing engagement with the valve ball. The shield extends from the valve ball to at least one of the inlet and the outlet and is adapted to channel the fluid therebetween. The valve stem operably engages the valve ball and is capable of actuating the valve ball between a position in which the fluid is capable of flowing between the inlet and the outlet through the bore in the valve ball and a position in which the fluid is not capable of flowing between the inlet and the outlet through the bore in the valve ball. The valve ball, the seat, the biasing device, and the shield, if included, are comprised of a refractory and/or toughened material such as, for example, a ceramic. In one particularly advantageous embodiment, the seat, the biasing device, and the shield, if present, are an integral structure fabricated from a unitary piece of a ceramic material such as, for example, yttria-stabilized zirconia.
Thus, the invention provides fluid-contacting and other components of a valve that are sufficiently flexible and generally heat and wear-resistant and can withstand significant applied tensile stresses. Certain components may be fabricated as unitary structures, thereby reducing the number of components required for the valve assembly. Embodiments of the invention therefore provide a valve capable of operating in high temperature and other hostile environments in a relatively safe and reliable manner, while the characteristics of the ceramic material facilitate cost-effective fabrication techniques. It will be recognized, therefore, that the invention facilitates the achievement of a number of distinct advantages over prior art valves used in high temperature or other hostile environments.